The invention relates to improvements in methods and apparatus for making reclosable bags and particularly in a form fill process wherein completed reopenable bags are formed by feeding film downwardly over a filling spout. More particularly, the invention relates to an improved manner in which completed packets or bags are formed with a reclosable zipper at the top edge and a safety seal joining the edges in an air-proof and moisture-proof seal outwardly of the reclosable zipper.
The art of making reclosable bags equipped with extruded plastic profile reclosable separable fastener means has experienced a long period of development as reflected in numerous patent disclosures. It has been conventional practice to extrude plastic material in tubular or sheet form with the profile separable fastener means co-extruded along and parallel to the longitudinal formation axis of the web, that is, the direction in which the web is extruded. On the other hand, prefabricated separable fastener strip means have been secured to separately formed web and with the fastener strip means extending longitudinally parallel to the longitudinal formation axis of the web. By way of example, U.S. Pat. Re. 29,043 is referred to as disclosing coextrusion of web and fastener means and forming the same into bag sections.
U.S. Pat. No. 3,948,705 exemplifies the technique of securing reclosable separable fastener strips to the plastic film parallel to the longitudinal formation axis of the web by fusion or heat seal methods.
Attachment of separable fastener strips parallel to the longitudinal formation of the axis of the web by adhesive means is exemplified in U.S. Pat. Nos. 4,372,793, 4,354,541 and 4,355,494.
U.S. Pat. No. 4,046,408 discloses separably interlockable fasteners along the edges of the plastic sheet material having generally arrow-shaped profiles, the fasteners being either integrally extruded from flat sheets or tubes of plastic film or supplied in the form of extruded strips attached to the web or film by heat sealing.
In the formation of reclosable plastic bags when the bags are used for foodstuffs and like material, it is advantageous to have the bags supplied with a tamper-proof seal which not only protects the contents from the ingress of foreign materials and contamination, but also prevents inadvertent or intentional opening prior to the bag and its contents being in the possession of the buyer. Such a protective seal if formed continuous externally of the reclosable seal can also protect the reclosable zipper elements from dust and dirt and other contaminants, with a permanent protective seal located outwardly of the reclosable seal, moisture and other foreign elements cannot enter the bag and the purchaser can see that he is obtaining a previously unopened and unused bag where the contents are fully protected. This conveys a feeling of safety and comfort to the purchaser who may be concerned about someone criminally obtaining access to the bag and placing dangerous contaminants into the contents.
Example of tamper-proof structures are shown in U.S. Pat. Nos. 2,978,769, 3,172,443, 3,685,562 and 3,780,781.